Muffler apparatus



Oct. I5, 1963 K. J. REcUPrro MUFFLER APPARATUS 2 sheets-sheet 1 Filed Deo. 5, 1960 Oct. 15, 1963 K- 1 RECUPlTQ 3,106,985

MUFFLER APPARATUS United States Patent Oflce 3,106,985 Patented Oct. 15, 1963 3,106,935 NUFFLER APPARATUS Kenneth I. Recupito, RU. Box 232, Lima, Pa. Filed Dec. 5, 1966, Ser. No. 73,804 Claims. (Cl. 18h-65) This invention relates to mufflers, and more particularly to exhaust gas mufflers.

Especially in exhaust mufiiers for internal combustion engines Iand the like, the effectiveness of a mufiier Idepends not only on its ability to accomplish silencing, but also on its ability to function Without building up back pressure to the extent that engine eficiency is reduced. Additionally, it is desirable that a muffler be compact.

The muffler of the present invention silences exhaust noises by repeated reflection of sound waves within a muffier, :and does not build up excessive back pressure, since the |mutlier and its outlet does not present a `restriction in the flow path of the exhaust gas.

A muffler constructed. according to the present invention comprises wall struct-ure defining an expansion charnber. There is also an inlet and a plurality of outlets for the expansion chamber. The flow area of each outlet is preferably at least as large as the flow are-a of the inlet, and there is valve structure associated with the outlets.

The valve structure includes first and second valves for respective. first and y,second outlets, each valve being resiliently mounted for movement between open and normally closed positions with respect to its associated valve. Preferably the second valve is resiliently mounted on the first valve; and the natural frequency of the first valve on its resilient mount is different from that of the second valve. The construction is such that the first valve is in resonance with engine vibrations during the operation thereof in one portion of its speed range, While the second valve is out of resonance and acts as a safety valve for the expansion chamber to relieve high pressures in the event of erratic engine operation. The functions of the valves are preferably interchanged at another portion of the engine speed range where the second valve is in resonance with engine vibrations and the first valve is not.

With this arrangement, the conventional method of opening valves by gas pressure is not employed except where one valve is employed as a safety valve. Instead, vibrational energy fof the engine is put to good use for opening and closing the valve in resonance therewith, thereby lQe-eping back pressure at a low level. With each exhaust pulsation the expansion chamber is completely closed while the sound Waves bounce thereabout 4and are attenuated before the slower traveling gases have reached the outlet, the valve in resonance opening before the next exhaust pulsation.

The various objects, features, and advantages of the invention will appear more fully from the following 1detailed description, taken in connection with the accompanying drawings, forming la part of this invention, in which:

FIG. l is an exploded perspective view of `a muffler embodying the invention and applied to an internal combustion engine which drives a chain saw;

FIG. 2 is a perspective viewl of the mufiler of FIG. `1 assembled, the engine and saw being shown fragmentarily;

FIG. 3 is an enlarged sca-le elevational View of the muffler as viewed from `the outlet side thereof, but with the cover removed;

FIG. 4 is a sectional view of the mufiler, taken on an enlarged scale along line IV-IV of FIG. 3, showing the parts in one operating position;

FIG. 5 is a view similar to FIG. 4, but showing the parts in another operating position;

FIG. 6 is a sectional view of the muffler, taken along line VI-VI of FIG. 3; yand FIG. 7 is a sectional view of the muffler, taken along line VlI-VII of FIG. 3.

The invention is well suited for mufflers of internal combustion engines and the like, especially two cycle enygines for driving portable tools including chain saws, and the invention is so illustrated. However, lthe invention is not so limited, since numerous other applications thereof are contemplated.

As shown in the drawings, the mufiier d'0 is mounted on a variable speed internal combustion engine 12, the latter being arranged in driving relationship with a chain saw 14. As best seen in FIG. 4, the muffler 10 includes rigid wall structure 16 defining an expansion chamber 18 having an inlet 20 communicating with the engine exhaust port 22. The muffler inlet 20` and the exhaust port 22 arek rigidly and tightly secured together, as 'by screws 24, to receive the engine exhaust gases. The wall `structure 16 further defines a large opening opposite the inlet 20 which is closed by a planar member 26 suitably secured to an outwardly projecting flange 28 of the wall structure. Preferably a gasket 30 is employed to ensure -a good seal between the flange 23 and the member 26.

The planar member 26 is provided with two outlets for the chamber 18, one of which comprises a group of holes 32 in a central region of the member 26 and designated as a Whole by the numeral 34. The other outlet in member 26 is designated by the numeral 36 and cornprises seriesfof holes 38 extending along both the upper and lower edges of member 26.

Associate-d with the outlets 34 and 36 is valve structure including a liminated valve plate 39, partly insulation 40 and partly metal sheet 41, but can be of unitary construction. The plate 39 is `apentured, having two series of holes 42 registering with the holes 312 of outlet 34 in member 26 to define therewith a passageway between the chamber 18 and the atmosphere; however, a valve 44 normally closes this passageway. The valve plate 39' is Ifurther provided with holes 46 arranged in two series, each series of holes 46 extending parallel to the holes 42 and out of registry with the holes 38 in member 26, preferably being aligned intermediate outlets 34 and 36 of member 26.

The valve plate 39 is biased toward the planar member 26 by bow springs 48 which can be made from flat stock of heat-resistant spring material, the springs 48 and the plate 39 being carried by a generally rectangularframe 50 attached to the back of the planar member 26. The springs 48 extend along the respective upper and lower edges of plate 39 and each is held captive within an elongated space defined between the frame SG and a bar 52 of L-shaped cross section, each bar being secured to the frame, as by screws 54. Strips 56 of insulation material are interposed between the springs 48 and the back of plate 39.

The valve 44 associated with the passageway defined bythe holes 32 and 42 comprises a laminated or sandwich constmction of a rigid rectangular sheet 60 between two similarly shaped sheets 6-2 of insulation material, but can be unitarily constructed, the sheets `6() `and 62 being received in a channel 64 of open work construction carried on fthe back of plate 39. yA bow spring 66 biases the valve 44 normally closed with respect to the passageway.

A decorative cover 68 is secured to the bars 52 and en- -closes the back of valve plate 39. It will be noted that `cover 68 has openings 69 which are large enough to permit the escape of exhaust gas without impedance, the total area of the openings 69 being at least as large as the flow area of the exhaust port 22 and inlet 26. Also, the flow tarea of the inlet 2f) is substantially the same as that of each of the outlets 34 and 36. Likewise, the holes 42 annesse provide the same flow area through plate 39 as do the holes 32 in member 26; and the holes 46 `correspond in ow area to the flow area of the holes 38. This provision, it will be seen, ensures that exhaust gases will not encounter a restricted flow path, 'whether they leave (the muffler solely through outlet 34 or solely through the outlet 36.

As best seen in FIGS. l, 2 and 6 the frame 5d is optionally provided with a multiplicity of tiny breather holes or restricted openings 7 (i which provide communication between the cool atmospheric air and the hot running parts of the muler.

The spring mounting system `for valve 44 is softer, or more easily deflected than the spring mounting system for the valve plate 39. This is accomplished by careful selection of the springs 4S and 66, with the result that the natural frequency of the valve 4d is appreciably lower than that of the valve plate 39. With this arrangement, valve 4d is in resonance Iwith the Vibrations produced by the engine in one portion of its speed range while the valve plate 39 is in resonance with the vibrations produced by the engine in another portion of its speed range.

In operation at low speed, for example, the valve 44 will oscillate between a normally closed position and an open position with respect to the outlet 34, and at the same time the valve plate 39 is biased against the planar member 26 to close the outlet 36. FIG. 4 illustrates the parts when the valve 44 is `opening the outlet 3d and the plate 39 is closing the outlet 36. During low speed operation, therefore, vibrational energy is employed to produce oscillating movement of valve 4d without reliance upon gas pressure to iiorce it open, thus avoiding a build up of back pressure. If some erratic running condition should produce a lbuild-up of high back pressure in the chamber 18 the valve d4 will continue alternately opening and closing outlet 34 without remaining open long enough to lower the pressure in chamber 1S. In Ithis situation the valve plate 39 will act as a safety valve to reduce back pressure while it is out of resonance with engine vibrations.

At another higher portion of the engine speed range, the unctions of the valve 44 and the valve plate 39 are interchanged. This is accomplished because valve plate 39 is mounted on stiffer springs 48 than the spring 66, and therefore has a higher natural lfrequency than valve 44. The valve plate 39 thus alternately opens and closes 'the outlet 36, oscillating in resonant response to the vibratory excitations of the engine; `and the valve 4d acts `at the same time as a safety Valve to relieve high back pressures in the chamber i8 through outlet 34..

Since the flow areas of the outlets 34 and 36 are at least as large as the iiow area of the inlet 20, and since the valve means which is in resonance with engine speed will open and close with each engine revolution, that is, once for each time there is a pulsation of exhaust gas discharged into the expansion chamber 1S. A build up of back pressure is unlikely.

It will be noted from the drawings that the valve plate 39 and the valve 44 both present flat surfaces to the expansion chamber 18, tending to reflect sound waves back into the expansion :chamber where they will continue to bounce about until attenuated. Thus attenuation of explosive sounds, which travel at very high speed, is accomplished While the slower traveling exhaust gas moves between the muffler inlet and the muliier outlet. Lt will also be noted that the valve plate 39 and the valve 44 when in open position, each define with its 4associated outlet a sinuous, but unrestricted exit path for exhaust gas. This provision of a sinuous exit path, taken with at valve surfaces presented at the outlets, provides a spark arrester for the engine, as well as a muffler. This spark arresting feature is of high commercial value to manufacturers of engine driven products, such as chain saws, because such products cannot be used lawfully in the d forests of many western states unless they `are capable of arresting sparks.

The compactness of the muflier disclosed herein is partly `attributable to the flat arrangement of the valves and the outlets. And flowing from this arrangement is the advantage that the outlets can be made up of small holes which convert some sounds in the audible range to inaudible sounds of higher frequency, thereby furthering the effectiveness of the muffler.

A muffler constructed `according to the present invention was found by test to reduce the sound level of a chain saw produced by `a leading manufacturer and equipped with la conventional muiiier as much as 22 idecibels at high speed and in the order of 12 decibels at low speed.

While the invention has been shown in but one form, it will be obvious to those skilled in the `art that it is not so limited, but is susceptible of various changes and modiications without departing from the spirit thereof.

What is claimed is:

l. A muflier for an internal combustion engine having exhaust means, which engine is operable in Va range of speeds and vibrates during operation at a `frequency proportional to engine oper-ating speed, said muiiier comprising wall structure deiininrg an expansion chamber, inlet means conneota-ble to said engine exhaust means for a lrnitting exhaust gas from said engine exhaust means to said chamber, a plurality of outlet means for gas being discharged from said chamber, a iirst valve operatively associated with one of said outlet means, a second valve operatively associated with the other of said outlet means, each of said valves being resiliently mounted on rigid structure and being vibratorily movable between open and closed positions with respect to its associated outlet means when vibratorily excited, the natural frequencies of vibration of said iirst and second valves being appreciably different whereby said irst valve is vibratorily excitable in one frequency range `and said second valve is vibratorily excitable in another lfrequency range, and means for `transmitting vibrations of said engine from said engine through the rigid structure on which said Valves are supported :to said valves, said iirst valve being operable by the vibrations of said engine in one portion of the engine speed range and said second valve being operable by the vibrations of said engine in another portion of the engine speed range.

2. A muiiier according to claim l wherein said other outlet means includes a passageway in said rst valve, and said second valve is mounted on said irst valve.

3. A muiiier for an internal combustion engine having exhaust means, which engine is oper-able in a range of speeds and vibrates during operation at a frequency propcrtional vto engine operating speed, said muffler cornprising wall structure defining an expansion chamber, inlet means connectable to said engine exhaust means for admitting exhaust gas from said engine to said chamber, iirst and second outlet means for gas being discharged from said chamber, each of said outlet means having a iiow area at least as large as the flow area of said inlet means, -a first valve operatively associated with said rst outlet means, a second valve operatively associated with said second outlet means, said iirst valve comprising a plate movable toward and away from said lirst outlet means when in operation, said plate in one position thereof having an imperforate portion in registry with said iirst outlet means and an apertured portion which is out of registry with said first outlet means, each of said valves being resiliently mounted on rigid structure and being movable lbetween open and closed positions with respect to its associated outlet means when vibratorily excited, the natural frequencies of vibration of said first and second valves being appreciable different whereby said first valve is vibratorily excitable in one yfrequency range and said second valve is vibratorily excitable in another frequency range, and means for transmitting viaio-5,985

brations of said engi-ne from said engine thro-ugh the rigid structure on which said valves are mounted to said valves, said first valve being operable by the vibrations of -said engine in one portion of the engine speed range and said second valve 'being operable by the vibrations of said engine in another portion-of the engine speed range.

4. The combination with an internal combustion engine having exhaust means, said engine being operable in a range of speeds and vibrating during operation at a frequency proportional to engine operating speed, of a muiiier comprising wall structure defining an expansion chamber, inlet means for admitting gas from said engine to said chamber, a plurality of outlet means for gas being discharged from said chamber, a first valve operatively associated with one of said outlet means, -a second valve operatively `associated with the other of said outlet means, each of said valves being resiliently mounted on rigid structure and being vibratorily movable between open and closed positions with respect to its associated outlet means when vibratorily excited, lthe natural frequencies of vibration of said irst and second valves being appreciably different whereby said first valve is vibratorily excited in one frequency range and said second valve is vibratorily excited in vanother frequency range, and means including Ia rigid connection between said engine exhaust means and said muier inlet means for transmitting Vibrations of said engine from said engine through rthe rigid structure on which said valves are mounted to said valves, said first valve being operable by the vibrations of said engine in one portion of the engine speed range and said second valve being operable by the vibration of said engine in :another portion of the engine speed range.

5. The combination with an internal combustion en gine having exhaust means, said engine being operable in a range of speeds and vibrating during operation at a frequency proportional to engine speed, of a mufiier comprising wall structure deiining an expansion chamber, inlet means for admitting gas from said engine exhaust means to said chamber, each of said outlet means having a flow area at least as large as the flow area of said iniet means, a iirst valve operatively associated with one of said outlet means, a second Valve operatively associated with the other Orf said outlet means, each of said valves being resiliently mounted on rigid structure and being vibratorily movable between open and closed positions with respect to its associated outlet means when vibratorily excited, the natural frequencies of vibration of said first and second val-ves being appreciably different whereby said first valve is vibratoriiy excitabie in one frequency range and said second valve is vibratorily excitable in another frequency range, and means including a rigid conneetion between said engine exhaust means and said muiiier inlet means for transmitting vibrations of said engine tfrom said engine through the rigid structure on :which said valves are mounted to said valves, said first valve being operable by the vibrations of said engine in one portion of the engine speed range and said second valve being operable by the vibrations of said engine in another portion of the engine speed range, each of said valves being normally closed when not moving vibratorily, each of said valves when not moving vibratorily opening under abnormally high gas pressure of a predetermined level in said chamber to reduce the pressure therein.

References Cited in the file of this patent UNITED STATES PATENTS 919,036 Langer Apr. 20, 1909 1,651,235 Terrilfl Nov. 29, 1927 1,673,619 Culp June 12, 1928 1,807,512 Culp May 26, 1931 FOREIGN PATENTS 301,556 Great Britain Dec. 6, 1928 752,641 Great Britain July 11, 1956 OTHER REFERENCES Noise Control, vol, 1, No. 4, issue of July 1955, pages 37-41 and 54, 

1. A MUFFLER FOR AN INTERNAL COMBUSTION ENGINE HAVING EXHAUST MEANS, WHICH ENGINE IS OPERABLE IN A RANGE OF SPEEDS AND VIBRATES DURING OPERATION AT A FREQUENCY PROPORTIONAL TO ENGINE OPERATING SPEED, SAID MUFFLER COMPRISING WALL STRUCTURE DEFINING AN EXPANSION CHAMBER, INLET MEANS CONNECTABLE TO SAID ENGINE EXHAUST MEANS FOR ADMITTING EXHAUST GAS FROM SAID ENGINE EXHAUST MEANS TO SAID CHAMBER, A PLURALITY OF OUTLET MEANS FOR GAS BEING DISCHARGED FROM SAID CHAMBER, A FIRST VALVE OPERATIVELY ASSOCIATED WITH ONE OF SAID OUTLET MEANS, A SECOND VALVE OPERATIVELY ASSOCIATED WITH THE OTHER OF SAID OUTLET MEANS, EACH OF SAID VALVES BEING RESILIENTLY MOUNTED ON RIGID STRUCTURE AND BEING VIBRATORILY MOVABLE BETWEEN OPEN AND CLOSED POSITIONS WITH RESPECT TO ITS ASSOCIATED OUTLET MEANS WHEN VIBRATORILY EXCITED, THE NATURAL FREQUENCIES OF VIBRATION OF SAID FIRST AND SECOND VALVES BEING APPRECIABLY DIFFERENT WHEREBY SAID FIRST VALVE IS VIBRATORILY EXCITABLE IN ONE FREQUENCY RANGE AND SAID SECOND VALVE IS VIBRATORILY EXCITABLE IN ANOTHER FREQUENCY RANGE, AND MEANS FOR TRANSMITTING VIBRATIONS OF SAID ENGINE FROM SAID ENGINE THROUGH THE RIGID STRUCTURE ON WHICH SAID VALVES ARE SUPPORTED TO SAID VALVES, SAID FIRST VALVE BEING OPERABLE BY THE VIBRATIONS OF SAID ENGINE IN ONE PORTION OF THE ENGINE SPEED RANGE AND SAID SECOND VALVE BEING OPERABLE BY THE VIBRATIONS OF SAID ENGINE IN ANOTHER PORTION OF THE ENGINE SPEED RANGE. 